The Malthusian trap, named after political economist Thomas Robert Malthus, suggests that for most of human history, income was largely stagnant because technological advances and discoveries only resulted in more people, rather than improvements in the standard of living. It is only with the onset of the Industrial Revolution in about 1800 that the income per person dramatically increased in some countries, and they broke out of the Trap; it has been shown, however, that the escape from the Malthusian trap can also generate serious political upheavals.
Malthus' theoretical argument
It was Thomas Malthus who first made the argument that in "every age and in every state" population increases are limited by the means of subsistence, and that when the means of subsistence increases, population will also increase, and that the population increase will be limited by "misery and vice". This pessimistic view on the impossibility of real progress was first made in 1798, ironically, just as the industrial revolution was getting underway.
In accordance with the theory, cross-country evidence indicates that technological superiority and higher land productivity had significant positive effects on population density but insignificant effects on the standard of living, during the time period 1–1500 AD. In addition, scholars have reported on the lack of a significant trend of wages in various places over the world for very long stretches of time. In Babylonia during the period 1800 to 1600 BC, for example, the daily wage for a common laborer was enough to buy about 15 pounds of wheat. In Classical Athens in about 328 BC, the corresponding wage could buy about 24 pounds of wheat. In England in 1800 AD the wage was about 13 pounds of wheat.:50 In spite of the technological developments across these societies, the daily wage hardly varied. In Britain between 1200 and 1800, only relatively minor fluctuations from the mean (less than a factor of two) in real wages occurred in Britain. They peaked at around 1450 and in 1800 they were actually significantly worse.
Robert Fogel published a study of lifespans and nutrition from about a century before Malthus to the 19th century that examined European birth and death records, military and other records of height and weight that found significant stunted height and low body weight indicative of chronic hunger and malnutrition. He also found short lifespans that he attributed to chronic malnourishment which left people susceptible to disease. Lifespans, height and weight began to steadily increase in the UK and France after 1750. Fogel's findings are consistent with estimates of available food supply.
Theories for the breakout
Causes for the Malthusian Trap and theories for the causes of the Industrial Revolution have been as multifarious as the theories of the fall of the Roman Empire. The transition from the Malthusian epoch to an era of sustained economic growth is explored by Unified growth theory. One branch of Unified growth theory is devoted to the interaction between human evolution and economic development. Some argue that natural selection during the Malthusian epoch selected beneficial traits to the growth process and brought about the Industrial Revolution. Consistent with the theory, evidence shows the survival of the richest in England during the 17th century.
From a macroeconomic perspective, the main contributions to the British breakout were technological improvements and structural change away from agricultural production, while coal, capital, and trade played a minor role.
A Trap at the escape from the Malthusian Trap
It has been recently suggested that the emergence of major sociopolitical upheavals at the escape from the Malthusian trap is not an abnormal, but a regular phenomenon.